And the great colour debate rages on. Much like the infamous dress that bitterly divided the internet back in February 2015, these Havaianas flip-flops have people flipping over what they see: white and gold or blue and brown.
When “the dress” first appeared, its poster, musician Caitlin McNeill, was legitimately looking for help identifying its colours. Twitter users across the globe, including celebs like Taylor Swift and Anna Kendrick, were vehemently divided — with some seeing it as blue and black, and others as white and gold.
Eventually, reporters turned to science to explain the discrepancy.
According to an article that appeared in Wired, it comes down to how the visual cortex of the brain processes the initial light that enters the retina. And because humans evolved to see things in daylight, which can change the colour of an image or item, the way we perceive colour is also informed by the light that’s around an object.
“What’s happening here is your visual system is looking at this thing, and you’re trying to discount the chromatic bias of the daylight axis,” said Bevil Conway, a neuroscientist who studies colour and vision at Wellesley College. “So people either discount the blue side, in which case they end up seeing white and gold, or discount the gold side, in which case they end up with blue and black.”
As it turned out, that particular dress was in fact blue and black.
A similar debate arose in October when a girl uploaded a picture of her legs streaked with white paint that to some looked like they were super shiny. That too was an optical illusion.
WATCH: The great dress debate.